The invention relates to a sliding door and particularly to the bottom rail of a sliding door to which there is attached a door structure of desired configuration which is caused to slide back and forth by means of a stationary drive motor unit, using a pinion that meshes with a gear rack attached to the door itself or to its bottom rail.
Sliding doors of the type under discussion can be guided and supported so as to roll on floor-located rails. They can also be moved into and out of their closed position without floor contact on guide sheaves which extend over only a fraction of the door panel's length, in the manner of a sliding gate. In any case, the respective drives for the types of doors here under discussion are stationary and use a drive pinion which meshes with a set of teeth that extends over the width of the door in its sliding direction (or rather the width of the opening to be closed off by the door) or as a minimum over the effective door displacement path.
Also known are comparably constructed friction drives in which, however, the friction drive wheel of the drive motor unit must contact under pressure a matching friction rail and the possibility of slippage between these two elements makes it difficult for this drive system to reproduce the desired displacement path.
From German patent publication (DE-AS) 1559961, it is known to have the drive pinion engage a metal gear rack, whose teeth are formed by milling, and which requires an additional, even more expensive treatment to give it the desired life span and trouble-free operation. Also, temperature variations along the rack cause trouble in meshing, and weather exposure causes rusting and resulting wear and tear, leading to correspondingly high maintenance requirements. Similar problems arise when a chain drive is used, because its engagement between driving and driven members is inherently imprecise, and ill-suited to smooth rolling, so that noise, wear and tear and rust, and resulting maintenance requirements are similar to those of the previously discussed rack.
It is also known, from German utility model (DE-GM) 8400934.9, to use, instead of a milled rack, a pre-tensioned, toothed belt, extending in the sliding direction of the door. Its flexibility makes it possible to wrap it around a wide angle of the drive pinion which meshes with the belt's teeth. Such an essentially unconstrained, toothed belt has to be able to absorb substantial pulling forces, and also presents guidance problems. Moreover, the desired wide wrap angle causes continuous flexing of the toothed belt. This could be avoided by using a rack made of a synthetic plastic but, in light of well-known considerations, this would again be difficult to manufacture as a single unit.